Process for the manufacture of partially saponified polyvinyl esters



Nov. 10, 1964 H. DEXHEIMER ETAL PROCESS FOR THE MANUFACTURE OF PARTIALLY Filed Aug. 10, 1961 SAPONIFIED POLYVINYL ESTERS 2 Sheets-Sheet 1 FIG].

' 80 mo 0F SUBSTANCE INTEGRAL DISTRIBUTION CURVE OF THE CHEMICAL COMPOSITION OF SOME PARTIALLY SAPONIFIED POLYVINYL ACETATES D-----IJ AVERAGE ACETYL CONTENT 2010 COMMERCIAL PRODUCT 25 7o ACCORDING TO INVENTION 16% INTERRUPTION OF REACTION 27% WITHOUT MIXING INVENTO RS H/I/VS DE/YHHMER OTTO FUCHS M/UMEZ ZEDEREI? IVEQ/IER .SCl/M/EDER ATTOR S 1964 H. DEXHEIMER ETAL PROCESS FOR THE MANUFACTURE OF PARTIALLY SAPONIFIED POLYVINYL ESTERS Filed Aug. 10, 1961 2 Sheets-Sheet 2 F/ '6. 2. i TEMF'.

cc UPPER TURBIDITY TEMPERATURE OF AQUEOUS SOLUTIONS OF PARTIALLY SAPONIFIED POLYVI NYL ACETATES E11 20% ACEVYL 25% ACETYL 1 2 CONC. /0

INVENTORS HANS DEXHE/MER OTTO FUCH-S MICHAEL LEDERER WERNER SCHMIEDER ATTORNE United States Patent 3,156,678 PRQtZESS FOR THE MANUFACTURE GF PAR- TIALLY SAPONIFIED POLYVINYL ESTERS Hans Dexheimer, Kelkheim, Taunus, Otto Fuchs, Hofheim, Taunus, Michael Lederer, Frankfurt am Mam, and Werner Sehrnieder, Hofheim, Taunus, Germany, assignors to Farbwerhe Hoeehst Aktiengesellschaft vormals Meister Lucius & Briining, Frankfurt am Main, Germany, a corporation of Germany Filed Aug. 10, 1961, Ser. No. 130,544 Claims priority, application Germany, Aug. 18, 1960, F 31,905 7 Claims. (Cl. 260-8.1)

The present invention relates to a process for the manufacture of partially saponified polyvinyl esters It is known to react a polyvinyl ester dissolved in an alcohol with catalytic amounts of sodium hydroxide or potassium hydroxide or sodium alcoholate or potassium alcoholate to obtain polyvinyl alcohol. Still further, it is known that by the addition of, for example, acid or water (British patent specifications Nos. 692,324 and 725,717) the reaction can be interrupted prematurely and a partially saponified polyvinyl ester can thus be prepared. Furthermore, it is known that part of the alcohol used for dissolution can be replaced by the corresponding ester formed in the reaction (cf. US. Patent 2,640,816) and by an appropriate selection of the composition of the batch the reaction can be brought to a premature standstill or considerably retarded, which facilitates a stop of the reaction. In the latter case, the viscosity of the batch passes during the reaction a steep maximum which is so high at a high polyvinyl ester concentrattion that during said phase the batch cannot be stirred. Since, however, a high concentration is desirable for obtaining a high spacetime yield, an intensive mixing is dispensed with (British specifications cited above). In a batch in which the degree of saponification can be adjusted by interrupting the reaction such a high maximum does not occur.

The methods described above yield chemically non uniform products. By, chemically uniform products there are to be understood products in which the ratio of the number of OH groups to the number of residual ester groups is constant in all macromolecules independent of their size. In contradistinction thereto said ratio varies within wide limits in non uniform products.

It has now been found that partially saponified polyvinyl esters, which have surprisingly a high chemical uniformity, can be obtained when a polyvinyl ester, which is dissolved in a solvent mixture containing an alcohol and the ester of said alcohol with the acid portion of said polyvinyl ester, is subjected to a partial alcoholysis in the presence of an alkaline catalyst and thus partially saponified. In the process of the invention the composition of the solvent mixture consisting of an alcohol, for example, methanol, ethanol or propanol, and the ester is chosen in a manner such that the proportion of ester to alcohol is 50:1 to 2.5:1 and preferably 6:1 to 3:1. The concentration of the polyvinyl ester, calculated on the total batch shall not exceed the Values defined in the following table which depend on the a red value of the polyvinyl ester (determined with a 1% solution of the polymer in ethyl acetate at 25 C. in an Gswald Viscometer). As catalyst there is used an alkali metal hydroxide, for example sodium or potassium hydroxide,

or an alkali metal alcoholate, for example sodium or potassium methylate, in an amount of about 0.1 to 2% and preferably 0.5 to 1%, calculated on the polyvinyl ester. The alcoholysis is carried out at a temperature between about 0 C. and the boiling point of the solvent mixture, advantageously between 10 and 30 C. in a practically anhyrous medium. Severe care is to be taken that during the whole period of reaction the mixture is but precipitated portions do not 3,156,678 Patented Nov. 10, 1964 "ice Maximum concentration of polyvinyl ester in the solution to be saponified:

1; Red value of polyvinyl ester 9 grams/ 100 cc. 2.45 16 grams/100 cc. 0.30 32 grams/100 cc. 0.41 42 grams/ 100 cc. 0.15

It results from the table that with an increasing 1 red value the concentration of the solution to be saponified must be reduced and vice versa. With the aid of the examples recited in the above table those skilled in the art will be in a position to find the maximum concentration of polyvinyl ester for a respective 1 red value.

In general the viscosity of a batch, determined at a drop in speed of D=88 sec in a rotation viscometer, shall not exceed in the course of the reaction a maximum value of 12,000 centipoises and preferably 8,000 centipoises.

On account of their high chemical uniformity the products of the invention have solubility properties that differ considerably from those of products prepared by known processes with reaction interruption or without permanent mixing as results from the following:

In the accompanying drawings FlGURE 1 represents for polyvinyl acetate the distribution curves of the chemical compositions of (a) a product produced without mixing, (b) a product made with interruption of the reaction, (c) a commercial product, and (d) a product obtained by the process of the invention. The curves were obtained in accordance with the indications in Verhandlungsberichte der Kolloid-Gesellschaft, volume 18 (1958), pages 81 by O. Fuchs. FIGURE 2 illustrates the differences in the solubility properties in water. It is known that partially saponified polyvinyl esters have a negative temperature coefficient of solubility in water, is. that they are soluble in the cold and precipitate on heating. In FIGURE 2 are plotted for various produtcs the temperatures above which the solution becomes turbid by precipitation (turbidity temperatures) against the concentration of the solution. Curve 1 is the curve of a commercial product containing 20% of acetyl (the chemical distribution of which is shown in curve c of FIGURE 1) and curves 2 to 4 are the curves of products prepared by the process of the invention and containing 21, 25 and 27.5% of acetyl, respectively. The minimum of the turbidity temperature of curve 1 is attributed to the chemical non uniformity and this is proved by the fact that a non uniform substance artificially prepared by mixing equal parts of three uniform substances having different acetyl contents has qualitatively the same behavior (curve 5) as the commercial product (curve 1).

The solubility effect represented in curves 24 compares favorably with that of curve 1 in that no precipitations can form on diluting with water. In the case of curve 1 a precipitation is formed when the solution is diluted, which leads to a non-homogeneous product. These inhomogeneities have a very unfavorable effect, for example in the manufacture of paints with the use of polyvinyl alcohols as thickening agents by the formation of lumps. When, for example, a solution of a product characterized by curve 1 and having a concentration and temperature as defined by point A is diluted the curve 1 is reached at point B and precipitation takes place up to point C. Below the concentration at point C the polyvinyl acetate is again soluble,

pass into solution immediately.

The process of the invention is applicable to a wide range of saponifiable polyvinyl esters, for example polymers of esters of vinyl alcohol with monobasic, saturated, aliphatic car-boxylic acids having 1 to 18 carbon atoms in a mum was reached and the batch became thinner while the turbidity remained. The reaction was terminated after 3 hours and the stirrer was switched off. The partially saponified polyvinyl acetate obtained still contained 28.1%

straight or branched chain, or polymers of esters of vinyl of residual acetyl. The batch could be stored without furalcohol with monobasic aromatic carboxylic acids. Suitther treatment without any modification of the product able polyvinyl esters are, for example, polyvinyl formate, taking place. The product could be converted into aquepolyvinyl propionate, polyvinyl butyrate, polyvinyl stearous solution by steam distillation or isolated by evaporaate, and polyvinyl benzoate. As polymers of vinyl esters tion. that are partially saponifiable there may furthermore be Example 2 ,F Y i' copglymers examfple. i The process was carried out as described in Example 1 W l 1; cope ymersfohvllly i with the same amounts of substances and at the same temvmy gi an e P t I mven Ion perature, with the exception that the polyvinyl acetate used can P y saporln 6 gm ymers g or had an 1 red value of 0.8. The solution obtained was i cstelrs Pg P i g considerably more viscous than the solution of Example exmilp a lffi 5 g f f: 1 and the viscosity maximum was higher, the time of re- X5 2 g yco f me 93 1 action being the same. The product had a residual acetyl g 3700' processo a lnventlon y.smta 6 content of 14.1%. The product obtained was likewise for the manufacture of partially sapomfied polyvinyl ace Stable in storage tate. The special composition of the total batch must be Example 3 empincally ad usted each time in a test series to the re- I ti polyvinyl ester 10 be i ll saponifie I The process was carried out as described n Example 1 general 1 batch contains the f llo i components; l with the exception that the solvent Was a mixture of 47.8 vinyl ester, for example polyvinyl acetate, alcohol, for ex- Parts Of methyl acetate, 759 Parts of {nfithahol and (H ample methanol, ester, for example methyl acetate, and the 25 Parts Wathr- The Product h a fesldhal acetylcomeht alkaline catalyst h degree of alcoholysis f the fi l of 34.6%. The product obtained was insoluble 1n water product can be varied within wide limits by an appropriate thus 3 P h hh transferred Into aqueous Sohlhofl y selection of the composition and the temperature of the a Steam dlstluatlohbatch Examples 4] 1 The Partially sfipohihed P y y esters P p Examples 4-11 were carried out in the same manner as P 'Q of invention are eslJechlhy Suitable E Examples 1 to 3. The variables are recited in the follow- ;hlckehlng agents In the mahllfactllm of aqueous P ing table. Each time part of the methanol indicated in the ormulations. fourth column was used for dissolving the sodium hydrox- The following examples serve to illustrate the invention, ide catalyst.

Methyl Methanol Water NaOI-I Tcmp., Residual No. Polyvinyl Acetate acetate parts part part C. acetyl, parts 1; red parts percent 10 0. 41 46 9. 4s 0. 1 0 20. 4 20 0. 41 46 11.15 0.1 25 34. 5 10 0. 41 49. 5 c. 92 0. 1 23 36. 3 10 0. 41 11.05 0 1 35 21.7 5 2. 45 4. 05 0. 05 25 24. 1 10 0. 41 45 0. 79 0. 1 25 45. 4 10 0. 41 41.9 12. 72 0. 1 23 4. 3 10 0.8 59 s. 0 0.1 25 2s. 4

but they are not intended to limit it thereto; the parts being Examples 12-14 by weight unless otherwise stated.

EM; l 1 These examples were carried out with a graft polymer e of 85% of vinyl acetate on 15% of polyethylene oxide In a vessel provided with a jacket for maintaining the (42.5% of acetyl) as described in the preceding examples.

Graft Methyl Methanol Water NaOl-I Temp, Residual N0. polymer acetate parts part part C. acetyl, parts parts percent temperature and a vigorous stirrer 10 parts of polyvinyl acetate (acetyl content 50%) having an 21 red value of 0.41 (determined with a 1% solution of the polymer in ethyl acetate at 25 C. in an Oswald viscometer) were dissolved while stirring in a mixture of 48.7 parts of methyl acetate and 6.8 parts of methanol. the solution was adjusted to 23 C. and a solution of 0.1 part of sodium hydroxide in 0.79 part of methanol was added. While continuously stirring, the reaction took place with a strong increase of the viscosity and the solu- The temperature of 7 0 Example 15 10 parts of a graft polymer of 50% of vinyl acetate on 50% of polyethylene oxide (25% of acetyl) were dissolved in 51 parts of methyl acetate and 6.3 parts of methanol and reacted in the presence of 0.1 part of NaOH as described in the preceding examples. The product obtained had a residual acetyl content of 14.5%.

Examples 16-18 A polyvinyl acetate having an 2; red value of 0.41 was 'tion became turbid, After 20 minutes the viscosity maXireacted in a mixture of ethanol and ethyl acetate as described in the preceding examples. listed in the following table.

The variables are Polyvinyl Ethyl Ethanol Water NaOH Temp, Residual No. acetate acetate parts part part C. acetyl,

parts parts percent Example 19 acetate with an alkaline catalyst in a substantially anhy- 10 parts of a polyvinyl acetate having an 1; red value of 0.41 were dissolved in a mixture of 42 parts of isopropyl acetate and 13.4 parts of iso-propanol and reacted as described in the preceding examples in the presence of 0.1 part of NaOH. The product obtained has a residual acetyl content of 14.5%.

We claim:

1. A process for the manufacture of a partially saponified polyvinyl ester which comprises stirring with an alkaline catalyst a polyvinyl ester in a solvent mixture consisting essentially of (1) an alcohol and (2) the ester of said alcohol and the acid portion of said polyvinyl ester while maintaining a ratio of component (2) to component (1) of the solvent mixture in the range between 50:1 and 2.511.

2. The process of claim 1 wherein the ratio of component (2) to component (1) of the solvent mixture is maintained in the range between 611 and 3:1.

3. The process of claim 1 wherein the polyvinyl ester is polyvinyl acetate.

drous solvent mixture consisting essentially of an alcohol and the acetic acid ester of said alcohol while maintaining the ratio of ester to alcohol in the range between about 5021 and 2.511.

5. The process defined in claim 4 wherein the alcohol is methanol and the ester is methyl acetate.

6. The process defined in claim 4- wherein the alcohol is ethanol and the ester is ethyl acetate.

7. The process defined in claim 4 wherein the alcohol is iso-propanol and the ester is iso-propyl acetate.

References Cited in the file of this patent UNITED STATES PATENTS 2,467,774 Plambeck Apr. 19, 1949 2,640,816 Germain June 2, 1953 2,940,948 Halbig et 'al June 14, 1960 3,036,054 Wheeler May 22, 1962 FOREIGN PATENTS 692,324 Great Britain June 3, 1953 725,717 Great Britain May 9, 1955 

1. A PROCESS FOR THE MANUFACTURE OF A PARTIALLY SAPONIFIED POLYVINYL ESTER WHICH COMPRISES STIRRING WITH AN ALKALINE CATALYST A POLYVINYL ESTER IN A SOLVENT MIXTURE CONSISTING ESSENTIALLY OF (1) AN ALCOHOL AND (2) THE ESTER OF SAID ALCOHOL AND THE ACID PORTION OF SAID POLYVINYL ESTER WHILE MAINTAINING A RATIO OF COMPONENT (2) TO COMPONENT (1) OF THE SOLVENT MIXTURE IN THE RANGE BETWEEN 50:1 TO 2.5:1. 